1. Field of the Invention
The present invention relates to a system, a method and a program for determining consistency of a database.
2. Description of the Related Art
In order to determine consistency of a database, it has conventionally been necessary to compare a storage address of each segment data included in the database and each pointer included in the database and to determine whether they coincide with each other. For example, such a consistency determination is implemented and used in a database management system developed by the present applicant. See, for example, “IMS High Performance Pointer Checker User's Guide, URL publibfi.boulder.ibm.com/cgi-bin/bookmgr/BOOKS/fabp lb 10/CCONTENTS”.
Here, when a database is updated between starting reading any one of the pointers and completely reading all the pointers, the segment data addresses may be compared with the pointers before and after updating. For this reason, during processing the determination of consistency, it has conventionally been general to stop updating a database or to perform exclusive control for access to at least a part of a database. See, for example, Japanese Published Patent Application No. 8-249222.
However, when the data size of a database is large, the updating may be stopped or delayed for a long time so that the user's convenience may be reduced. In contrast, a technique for determining consistency without stopping the updating is proposed as disclosed, for example, in Japanese Published Patent Application No. 2001-142765.
According to a technique disclosed in Japanese Published Patent Application No. 2001-142765, a consistency verifying apparatus takes out data for use in consistency verification from a database file without performing exclusive control. Then, the consistency verifying apparatus repeats the process for performing the consistency verification using the taken-out data by a predetermined number of times, and determines whether the database file is consistent based on the verification result of the process and a preset condition for determining the consistency. Therefore, it is considered that, according to this technique, a possibility of satisfying the consistency can be evaluated, but it is not possible to surely determine the consistency. From a different viewpoint, the number of times for performing the consistency verification should be increased to surely determine the consistency, which would result in a longer processing time.